This K&N Stubstack is designed to be used on Demon 750/850 carburetors. The full radius design helps to increase the airflow for drag racing. Will also hold down the baseplate of a cold air scoop. Will not work with K&N Custom Chrome Racing Air Cleaners. The K&N Stubstack is designed to increase the airflow of carburetors by decreasing the restriction around the choke horn. The stubstack fits inside the air cleaner housing and slides snugly down over the choke horn.